Java Day 6: Arrays

Goal of this Day

Today you will learn:

• How to declare and initialize arrays
• How to access elements in an array
• How to loop through arrays
• Common operations with arrays

By the end, you will be able to store and manage multiple values using arrays.

Step 1: Declaring and Initializing Arrays

An array stores multiple values of the same type.

int[] numbers = {1, 2, 3, 4, 5};

Explanation:

• int[] → defines an array of integers
• { } → contains the values

Step 2: Accessing Elements

You can access elements using their index.

System.out.println(numbers[0]); // first element
System.out.println(numbers[2]); // third element

Note: Arrays start at index 0.

Step 3: Iterating Through Arrays

You can loop through arrays using loops.

For Loop

for(int i = 0; i < numbers.length; i++) {
    System.out.println(numbers[i]);
}

Enhanced For Loop (for-each)

for(int num : numbers) {
    System.out.println(num);
}

Step 4: Common Array Operations

Some common tasks with arrays include:

• Finding the largest value
• Finding the smallest value
• Calculating the sum

Example (sum):

int sum = 0;

for(int num : numbers) {
    sum += num;
}

System.out.println("Sum: " + sum);

Practice

int[] numbers = {1, 2, 3, 4, 5};

for(int num : numbers) {
    System.out.println(num);
}

Exercise

Write a program that finds the largest number in an array.

Steps:

• Create an array with numbers
• Use a loop to go through the array
• Store the largest number in a variable
• Print the result

Example:

public class LargestNumber {
    public static void main(String[] args) {
        int[] numbers = {4, 7, 1, 9, 3};

        int largest = numbers[0];

        for(int num : numbers) {
            if(num > largest) {
                largest = num;
            }
        }

        System.out.println("Largest number: " + largest);
    }
}